balloc.c

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/*
 *  linux/fs/ext3/balloc.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card ([email protected])
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  Enhanced block allocation by Stephen Tweedie ([email protected]), 1993
 *  Big-endian to little-endian byte-swapping/bitmaps by
 *        David S. Miller ([email protected]), 1995
 */

#include <linux/quotaops.h>
#include <linux/blkdev.h>
#include "ext3.h"

/*
 * balloc.c contains the blocks allocation and deallocation routines
 */

/*
 * The free blocks are managed by bitmaps.  A file system contains several
 * blocks groups.  Each group contains 1 bitmap block for blocks, 1 bitmap
 * block for inodes, N blocks for the inode table and data blocks.
 *
 * The file system contains group descriptors which are located after the
 * super block.  Each descriptor contains the number of the bitmap block and
 * the free blocks count in the block.  The descriptors are loaded in memory
 * when a file system is mounted (see ext3_fill_super).
 */


#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)

/*
 * Calculate the block group number and offset, given a block number
 */
static void ext3_get_group_no_and_offset(struct super_block *sb,
    ext3_fsblk_t blocknr, unsigned long *blockgrpp, ext3_grpblk_t *offsetp)
{
    struct ext3_super_block *es = EXT3_SB(sb)->s_es;

    blocknr = blocknr - le32_to_cpu(es->s_first_data_block);
    if (offsetp)
        *offsetp = blocknr % EXT3_BLOCKS_PER_GROUP(sb);
    if (blockgrpp)
        *blockgrpp = blocknr / EXT3_BLOCKS_PER_GROUP(sb);
}

struct ext3_group_desc * ext3_get_group_desc(struct super_block * sb,
                         unsigned int block_group,
                         struct buffer_head ** bh)
{
    unsigned long group_desc;
    unsigned long offset;
    struct ext3_group_desc * desc;
    struct ext3_sb_info *sbi = EXT3_SB(sb);

    if (block_group >= sbi->s_groups_count) {
        ext3_error (sb, "ext3_get_group_desc",
                "block_group >= groups_count - "
                "block_group = %d, groups_count = %lu",
                block_group, sbi->s_groups_count);

        return NULL;
    }
    smp_rmb();

    group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(sb);
    offset = block_group & (EXT3_DESC_PER_BLOCK(sb) - 1);
    if (!sbi->s_group_desc[group_desc]) {
        ext3_error (sb, "ext3_get_group_desc",
                "Group descriptor not loaded - "
                "block_group = %d, group_desc = %lu, desc = %lu",
                 block_group, group_desc, offset);
        return NULL;
    }

    desc = (struct ext3_group_desc *) sbi->s_group_desc[group_desc]->b_data;
    if (bh)
        *bh = sbi->s_group_desc[group_desc];
    return desc + offset;
}

static int ext3_valid_block_bitmap(struct super_block *sb,
                    struct ext3_group_desc *desc,
                    unsigned int block_group,
                    struct buffer_head *bh)
{
    ext3_grpblk_t offset;
    ext3_grpblk_t next_zero_bit;
    ext3_fsblk_t bitmap_blk;
    ext3_fsblk_t group_first_block;

    group_first_block = ext3_group_first_block_no(sb, block_group);

    /* check whether block bitmap block number is set */
    bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
    offset = bitmap_blk - group_first_block;
    if (!ext3_test_bit(offset, bh->b_data))
        /* bad block bitmap */
        goto err_out;

    /* check whether the inode bitmap block number is set */
    bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
    offset = bitmap_blk - group_first_block;
    if (!ext3_test_bit(offset, bh->b_data))
        /* bad block bitmap */
        goto err_out;

    /* check whether the inode table block number is set */
    bitmap_blk = le32_to_cpu(desc->bg_inode_table);
    offset = bitmap_blk - group_first_block;
    next_zero_bit = ext3_find_next_zero_bit(bh->b_data,
                offset + EXT3_SB(sb)->s_itb_per_group,
                offset);
    if (next_zero_bit >= offset + EXT3_SB(sb)->s_itb_per_group)
        /* good bitmap for inode tables */
        return 1;

err_out:
    ext3_error(sb, __func__,
            "Invalid block bitmap - "
            "block_group = %d, block = %lu",
            block_group, bitmap_blk);
    return 0;
}

static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
    struct ext3_group_desc * desc;
    struct buffer_head * bh = NULL;
    ext3_fsblk_t bitmap_blk;

    desc = ext3_get_group_desc(sb, block_group, NULL);
    if (!desc)
        return NULL;
    trace_ext3_read_block_bitmap(sb, block_group);
    bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
    bh = sb_getblk(sb, bitmap_blk);
    if (unlikely(!bh)) {
        ext3_error(sb, __func__,
                "Cannot read block bitmap - "
                "block_group = %d, block_bitmap = %u",
                block_group, le32_to_cpu(desc->bg_block_bitmap));
        return NULL;
    }
    if (likely(bh_uptodate_or_lock(bh)))
        return bh;

    if (bh_submit_read(bh) < 0) {
        brelse(bh);
        ext3_error(sb, __func__,
                "Cannot read block bitmap - "
                "block_group = %d, block_bitmap = %u",
                block_group, le32_to_cpu(desc->bg_block_bitmap));
        return NULL;
    }
    ext3_valid_block_bitmap(sb, desc, block_group, bh);
    /*
     * file system mounted not to panic on error, continue with corrupt
     * bitmap
     */
    return bh;
}
/*
 * The reservation window structure operations
 * --------------------------------------------
 * Operations include:
 * dump, find, add, remove, is_empty, find_next_reservable_window, etc.
 *
 * We use a red-black tree to represent per-filesystem reservation
 * windows.
 *
 */

#if 1
static void __rsv_window_dump(struct rb_root *root, int verbose,
                  const char *fn)
{
    struct rb_node *n;
    struct ext3_reserve_window_node *rsv, *prev;
    int bad;

restart:
    n = rb_first(root);
    bad = 0;
    prev = NULL;

    printk("Block Allocation Reservation Windows Map (%s):\n", fn);
    while (n) {
        rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
        if (verbose)
            printk("reservation window 0x%p "
                   "start:  %lu, end:  %lu\n",
                   rsv, rsv->rsv_start, rsv->rsv_end);
        if (rsv->rsv_start && rsv->rsv_start >= rsv->rsv_end) {
            printk("Bad reservation %p (start >= end)\n",
                   rsv);
            bad = 1;
        }
        if (prev && prev->rsv_end >= rsv->rsv_start) {
            printk("Bad reservation %p (prev->end >= start)\n",
                   rsv);
            bad = 1;
        }
        if (bad) {
            if (!verbose) {
                printk("Restarting reservation walk in verbose mode\n");
                verbose = 1;
                goto restart;
            }
        }
        n = rb_next(n);
        prev = rsv;
    }
    printk("Window map complete.\n");
    BUG_ON(bad);
}
#define rsv_window_dump(root, verbose) \
    __rsv_window_dump((root), (verbose), __func__)
#else
#define rsv_window_dump(root, verbose) do {} while (0)
#endif

static int
goal_in_my_reservation(struct ext3_reserve_window *rsv, ext3_grpblk_t grp_goal,
            unsigned int group, struct super_block * sb)
{
    ext3_fsblk_t group_first_block, group_last_block;

    group_first_block = ext3_group_first_block_no(sb, group);
    group_last_block = group_first_block + (EXT3_BLOCKS_PER_GROUP(sb) - 1);

    if ((rsv->_rsv_start > group_last_block) ||
        (rsv->_rsv_end < group_first_block))
        return 0;
    if ((grp_goal >= 0) && ((grp_goal + group_first_block < rsv->_rsv_start)
        || (grp_goal + group_first_block > rsv->_rsv_end)))
        return 0;
    return 1;
}

static struct ext3_reserve_window_node *
search_reserve_window(struct rb_root *root, ext3_fsblk_t goal)
{
    struct rb_node *n = root->rb_node;
    struct ext3_reserve_window_node *rsv;

    if (!n)
        return NULL;

    do {
        rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);

        if (goal < rsv->rsv_start)
            n = n->rb_left;
        else if (goal > rsv->rsv_end)
            n = n->rb_right;
        else
            return rsv;
    } while (n);
    /*
     * We've fallen off the end of the tree: the goal wasn't inside
     * any particular node.  OK, the previous node must be to one
     * side of the interval containing the goal.  If it's the RHS,
     * we need to back up one.
     */
    if (rsv->rsv_start > goal) {
        n = rb_prev(&rsv->rsv_node);
        rsv = rb_entry(n, struct ext3_reserve_window_node, rsv_node);
    }
    return rsv;
}

void ext3_rsv_window_add(struct super_block *sb,
            struct ext3_reserve_window_node *rsv)
{
    struct rb_root *root = &EXT3_SB(sb)->s_rsv_window_root;
    struct rb_node *node = &rsv->rsv_node;
    ext3_fsblk_t start = rsv->rsv_start;

    struct rb_node ** p = &root->rb_node;
    struct rb_node * parent = NULL;
    struct ext3_reserve_window_node *this;

    trace_ext3_rsv_window_add(sb, rsv);
    while (*p)
    {
        parent = *p;
        this = rb_entry(parent, struct ext3_reserve_window_node, rsv_node);

        if (start < this->rsv_start)
            p = &(*p)->rb_left;
        else if (start > this->rsv_end)
            p = &(*p)->rb_right;
        else {
            rsv_window_dump(root, 1);
            BUG();
        }
    }

    rb_link_node(node, parent, p);
    rb_insert_color(node, root);
}

static void rsv_window_remove(struct super_block *sb,
                  struct ext3_reserve_window_node *rsv)
{
    rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
    rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
    rsv->rsv_alloc_hit = 0;
    rb_erase(&rsv->rsv_node, &EXT3_SB(sb)->s_rsv_window_root);
}

/*
 * rsv_is_empty() -- Check if the reservation window is allocated.
 * @rsv:        given reservation window to check
 *
 * returns 1 if the end block is EXT3_RESERVE_WINDOW_NOT_ALLOCATED.
 */
static inline int rsv_is_empty(struct ext3_reserve_window *rsv)
{
    /* a valid reservation end block could not be 0 */
    return rsv->_rsv_end == EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
}

void ext3_init_block_alloc_info(struct inode *inode)
{
    struct ext3_inode_info *ei = EXT3_I(inode);
    struct ext3_block_alloc_info *block_i;
    struct super_block *sb = inode->i_sb;

    block_i = kmalloc(sizeof(*block_i), GFP_NOFS);
    if (block_i) {
        struct ext3_reserve_window_node *rsv = &block_i->rsv_window_node;

        rsv->rsv_start = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;
        rsv->rsv_end = EXT3_RESERVE_WINDOW_NOT_ALLOCATED;

        /*
         * if filesystem is mounted with NORESERVATION, the goal
         * reservation window size is set to zero to indicate
         * block reservation is off
         */
        if (!test_opt(sb, RESERVATION))
            rsv->rsv_goal_size = 0;
        else
            rsv->rsv_goal_size = EXT3_DEFAULT_RESERVE_BLOCKS;
        rsv->rsv_alloc_hit = 0;
        block_i->last_alloc_logical_block = 0;
        block_i->last_alloc_physical_block = 0;
    }
    ei->i_block_alloc_info = block_i;
}

void ext3_discard_reservation(struct inode *inode)
{
    struct ext3_inode_info *ei = EXT3_I(inode);
    struct ext3_block_alloc_info *block_i = ei->i_block_alloc_info;
    struct ext3_reserve_window_node *rsv;
    spinlock_t *rsv_lock = &EXT3_SB(inode->i_sb)->s_rsv_window_lock;

    if (!block_i)
        return;

    rsv = &block_i->rsv_window_node;
    if (!rsv_is_empty(&rsv->rsv_window)) {
        spin_lock(rsv_lock);
        if (!rsv_is_empty(&rsv->rsv_window)) {
            trace_ext3_discard_reservation(inode, rsv);
            rsv_window_remove(inode->i_sb, rsv);
        }
        spin_unlock(rsv_lock);
    }
}

void ext3_free_blocks_sb(handle_t *handle, struct super_block *sb,
             ext3_fsblk_t block, unsigned long count,
             unsigned long *pdquot_freed_blocks)
{
    struct buffer_head *bitmap_bh = NULL;
    struct buffer_head *gd_bh;
    unsigned long block_group;
    ext3_grpblk_t bit;
    unsigned long i;
    unsigned long overflow;
    struct ext3_group_desc * desc;
    struct ext3_super_block * es;
    struct ext3_sb_info *sbi;
    int err = 0, ret;
    ext3_grpblk_t group_freed;

    *pdquot_freed_blocks = 0;
    sbi = EXT3_SB(sb);
    es = sbi->s_es;
    if (block < le32_to_cpu(es->s_first_data_block) ||
        block + count < block ||
        block + count > le32_to_cpu(es->s_blocks_count)) {
        ext3_error (sb, "ext3_free_blocks",
                "Freeing blocks not in datazone - "
                "block = "E3FSBLK", count = %lu", block, count);
        goto error_return;
    }

    ext3_debug ("freeing block(s) %lu-%lu\n", block, block + count - 1);

do_more:
    overflow = 0;
    block_group = (block - le32_to_cpu(es->s_first_data_block)) /
              EXT3_BLOCKS_PER_GROUP(sb);
    bit = (block - le32_to_cpu(es->s_first_data_block)) %
              EXT3_BLOCKS_PER_GROUP(sb);
    /*
     * Check to see if we are freeing blocks across a group
     * boundary.
     */
    if (bit + count > EXT3_BLOCKS_PER_GROUP(sb)) {
        overflow = bit + count - EXT3_BLOCKS_PER_GROUP(sb);
        count -= overflow;
    }
    brelse(bitmap_bh);
    bitmap_bh = read_block_bitmap(sb, block_group);
    if (!bitmap_bh)
        goto error_return;
    desc = ext3_get_group_desc (sb, block_group, &gd_bh);
    if (!desc)
        goto error_return;

    if (in_range (le32_to_cpu(desc->bg_block_bitmap), block, count) ||
        in_range (le32_to_cpu(desc->bg_inode_bitmap), block, count) ||
        in_range (block, le32_to_cpu(desc->bg_inode_table),
              sbi->s_itb_per_group) ||
        in_range (block + count - 1, le32_to_cpu(desc->bg_inode_table),
              sbi->s_itb_per_group)) {
        ext3_error (sb, "ext3_free_blocks",
                "Freeing blocks in system zones - "
                "Block = "E3FSBLK", count = %lu",
                block, count);
        goto error_return;
    }

    /*
     * We are about to start releasing blocks in the bitmap,
     * so we need undo access.
     */
    /* @@@ check errors */
    BUFFER_TRACE(bitmap_bh, "getting undo access");
    err = ext3_journal_get_undo_access(handle, bitmap_bh);
    if (err)
        goto error_return;

    /*
     * We are about to modify some metadata.  Call the journal APIs
     * to unshare ->b_data if a currently-committing transaction is
     * using it
     */
    BUFFER_TRACE(gd_bh, "get_write_access");
    err = ext3_journal_get_write_access(handle, gd_bh);
    if (err)
        goto error_return;

    jbd_lock_bh_state(bitmap_bh);

    for (i = 0, group_freed = 0; i < count; i++) {
        /*
         * An HJ special.  This is expensive...
         */
#ifdef CONFIG_JBD_DEBUG
        jbd_unlock_bh_state(bitmap_bh);
        {
            struct buffer_head *debug_bh;
            debug_bh = sb_find_get_block(sb, block + i);
            if (debug_bh) {
                BUFFER_TRACE(debug_bh, "Deleted!");
                if (!bh2jh(bitmap_bh)->b_committed_data)
                    BUFFER_TRACE(debug_bh,
                        "No committed data in bitmap");
                BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap");
                __brelse(debug_bh);
            }
        }
        jbd_lock_bh_state(bitmap_bh);
#endif
        if (need_resched()) {
            jbd_unlock_bh_state(bitmap_bh);
            cond_resched();
            jbd_lock_bh_state(bitmap_bh);
        }
        /* @@@ This prevents newly-allocated data from being
         * freed and then reallocated within the same
         * transaction.
         *
         * Ideally we would want to allow that to happen, but to
         * do so requires making journal_forget() capable of
         * revoking the queued write of a data block, which
         * implies blocking on the journal lock.  *forget()
         * cannot block due to truncate races.
         *
         * Eventually we can fix this by making journal_forget()
         * return a status indicating whether or not it was able
         * to revoke the buffer.  On successful revoke, it is
         * safe not to set the allocation bit in the committed
         * bitmap, because we know that there is no outstanding
         * activity on the buffer any more and so it is safe to
         * reallocate it.
         */
        BUFFER_TRACE(bitmap_bh, "set in b_committed_data");
        J_ASSERT_BH(bitmap_bh,
                bh2jh(bitmap_bh)->b_committed_data != NULL);
        ext3_set_bit_atomic(sb_bgl_lock(sbi, block_group), bit + i,
                bh2jh(bitmap_bh)->b_committed_data);

        /*
         * We clear the bit in the bitmap after setting the committed
         * data bit, because this is the reverse order to that which
         * the allocator uses.
         */
        BUFFER_TRACE(bitmap_bh, "clear bit");
        if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, block_group),
                        bit + i, bitmap_bh->b_data)) {
            jbd_unlock_bh_state(bitmap_bh);
            ext3_error(sb, __func__,
                "bit already cleared for block "E3FSBLK,
                 block + i);
            jbd_lock_bh_state(bitmap_bh);
            BUFFER_TRACE(bitmap_bh, "bit already cleared");
        } else {
            group_freed++;
        }
    }
    jbd_unlock_bh_state(bitmap_bh);

    spin_lock(sb_bgl_lock(sbi, block_group));
    le16_add_cpu(&desc->bg_free_blocks_count, group_freed);
    spin_unlock(sb_bgl_lock(sbi, block_group));
    percpu_counter_add(&sbi->s_freeblocks_counter, count);

    /* We dirtied the bitmap block */
    BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
    err = ext3_journal_dirty_metadata(handle, bitmap_bh);

    /* And the group descriptor block */
    BUFFER_TRACE(gd_bh, "dirtied group descriptor block");
    ret = ext3_journal_dirty_metadata(handle, gd_bh);
    if (!err) err = ret;
    *pdquot_freed_blocks += group_freed;

    if (overflow && !err) {
        block += count;
        count = overflow;
        goto do_more;
    }

error_return:
    brelse(bitmap_bh);
    ext3_std_error(sb, err);
    return;
}

void ext3_free_blocks(handle_t *handle, struct inode *inode,
            ext3_fsblk_t block, unsigned long count)
{
    struct super_block *sb = inode->i_sb;
    unsigned long dquot_freed_blocks;

    trace_ext3_free_blocks(inode, block, count);
    ext3_free_blocks_sb(handle, sb, block, count, &dquot_freed_blocks);
    if (dquot_freed_blocks)
        dquot_free_block(inode, dquot_freed_blocks);
    return;
}

static int ext3_test_allocatable(ext3_grpblk_t nr, struct buffer_head *bh)
{
    int ret;
    struct journal_head *jh = bh2jh(bh);

    if (ext3_test_bit(nr, bh->b_data))
        return 0;

    jbd_lock_bh_state(bh);
    if (!jh->b_committed_data)
        ret = 1;
    else
        ret = !ext3_test_bit(nr, jh->b_committed_data);
    jbd_unlock_bh_state(bh);
    return ret;
}

static ext3_grpblk_t
bitmap_search_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
                    ext3_grpblk_t maxblocks)
{
    ext3_grpblk_t next;
    struct journal_head *jh = bh2jh(bh);

    while (start < maxblocks) {
        next = ext3_find_next_zero_bit(bh->b_data, maxblocks, start);
        if (next >= maxblocks)
            return -1;
        if (ext3_test_allocatable(next, bh))
            return next;
        jbd_lock_bh_state(bh);
        if (jh->b_committed_data)
            start = ext3_find_next_zero_bit(jh->b_committed_data,
                            maxblocks, next);
        jbd_unlock_bh_state(bh);
    }
    return -1;
}

static ext3_grpblk_t
find_next_usable_block(ext3_grpblk_t start, struct buffer_head *bh,
            ext3_grpblk_t maxblocks)
{
    ext3_grpblk_t here, next;
    char *p, *r;

    if (start > 0) {
        /*
         * The goal was occupied; search forward for a free
         * block within the next XX blocks.
         *
         * end_goal is more or less random, but it has to be
         * less than EXT3_BLOCKS_PER_GROUP. Aligning up to the
         * next 64-bit boundary is simple..
         */
        ext3_grpblk_t end_goal = (start + 63) & ~63;
        if (end_goal > maxblocks)
            end_goal = maxblocks;
        here = ext3_find_next_zero_bit(bh->b_data, end_goal, start);
        if (here < end_goal && ext3_test_allocatable(here, bh))
            return here;
        ext3_debug("Bit not found near goal\n");
    }

    here = start;
    if (here < 0)
        here = 0;

    p = bh->b_data + (here >> 3);
    r = memscan(p, 0, ((maxblocks + 7) >> 3) - (here >> 3));
    next = (r - bh->b_data) << 3;

    if (next < maxblocks && next >= start && ext3_test_allocatable(next, bh))
        return next;

    /*
     * The bitmap search --- search forward alternately through the actual
     * bitmap and the last-committed copy until we find a bit free in
     * both
     */
    here = bitmap_search_next_usable_block(here, bh, maxblocks);
    return here;
}

static inline int
claim_block(spinlock_t *lock, ext3_grpblk_t block, struct buffer_head *bh)
{
    struct journal_head *jh = bh2jh(bh);
    int ret;

    if (ext3_set_bit_atomic(lock, block, bh->b_data))
        return 0;
    jbd_lock_bh_state(bh);
    if (jh->b_committed_data && ext3_test_bit(block,jh->b_committed_data)) {
        ext3_clear_bit_atomic(lock, block, bh->b_data);
        ret = 0;
    } else {
        ret = 1;
    }
    jbd_unlock_bh_state(bh);
    return ret;
}

static ext3_grpblk_t
ext3_try_to_allocate(struct super_block *sb, handle_t *handle, int group,
            struct buffer_head *bitmap_bh, ext3_grpblk_t grp_goal,
            unsigned long *count, struct ext3_reserve_window *my_rsv)
{
    ext3_fsblk_t group_first_block;
    ext3_grpblk_t start, end;
    unsigned long num = 0;

    /* we do allocation within the reservation window if we have a window */
    if (my_rsv) {
        group_first_block = ext3_group_first_block_no(sb, group);
        if (my_rsv->_rsv_start >= group_first_block)
            start = my_rsv->_rsv_start - group_first_block;
        else
            /* reservation window cross group boundary */
            start = 0;
        end = my_rsv->_rsv_end - group_first_block + 1;
        if (end > EXT3_BLOCKS_PER_GROUP(sb))
            /* reservation window crosses group boundary */
            end = EXT3_BLOCKS_PER_GROUP(sb);
        if ((start <= grp_goal) && (grp_goal < end))
            start = grp_goal;
        else
            grp_goal = -1;
    } else {
        if (grp_goal > 0)
            start = grp_goal;
        else
            start = 0;
        end = EXT3_BLOCKS_PER_GROUP(sb);
    }

    BUG_ON(start > EXT3_BLOCKS_PER_GROUP(sb));

repeat:
    if (grp_goal < 0 || !ext3_test_allocatable(grp_goal, bitmap_bh)) {
        grp_goal = find_next_usable_block(start, bitmap_bh, end);
        if (grp_goal < 0)
            goto fail_access;
        if (!my_rsv) {
            int i;

            for (i = 0; i < 7 && grp_goal > start &&
                    ext3_test_allocatable(grp_goal - 1,
                                bitmap_bh);
                    i++, grp_goal--)
                ;
        }
    }
    start = grp_goal;

    if (!claim_block(sb_bgl_lock(EXT3_SB(sb), group),
        grp_goal, bitmap_bh)) {
        /*
         * The block was allocated by another thread, or it was
         * allocated and then freed by another thread
         */
        start++;
        grp_goal++;
        if (start >= end)
            goto fail_access;
        goto repeat;
    }
    num++;
    grp_goal++;
    while (num < *count && grp_goal < end
        && ext3_test_allocatable(grp_goal, bitmap_bh)
        && claim_block(sb_bgl_lock(EXT3_SB(sb), group),
                grp_goal, bitmap_bh)) {
        num++;
        grp_goal++;
    }
    *count = num;
    return grp_goal - num;
fail_access:
    *count = num;
    return -1;
}

static int find_next_reservable_window(
                struct ext3_reserve_window_node *search_head,
                struct ext3_reserve_window_node *my_rsv,
                struct super_block * sb,
                ext3_fsblk_t start_block,
                ext3_fsblk_t last_block)
{
    struct rb_node *next;
    struct ext3_reserve_window_node *rsv, *prev;
    ext3_fsblk_t cur;
    int size = my_rsv->rsv_goal_size;

    /* TODO: make the start of the reservation window byte-aligned */
    /* cur = *start_block & ~7;*/
    cur = start_block;
    rsv = search_head;
    if (!rsv)
        return -1;

    while (1) {
        if (cur <= rsv->rsv_end)
            cur = rsv->rsv_end + 1;

        /* TODO?
         * in the case we could not find a reservable space
         * that is what is expected, during the re-search, we could
         * remember what's the largest reservable space we could have
         * and return that one.
         *
         * For now it will fail if we could not find the reservable
         * space with expected-size (or more)...
         */
        if (cur > last_block)
            return -1;      /* fail */

        prev = rsv;
        next = rb_next(&rsv->rsv_node);
        rsv = rb_entry(next,struct ext3_reserve_window_node,rsv_node);

        /*
         * Reached the last reservation, we can just append to the
         * previous one.
         */
        if (!next)
            break;

        if (cur + size <= rsv->rsv_start) {
            /*
             * Found a reserveable space big enough.  We could
             * have a reservation across the group boundary here
             */
            break;
        }
    }
    /*
     * we come here either :
     * when we reach the end of the whole list,
     * and there is empty reservable space after last entry in the list.
     * append it to the end of the list.
     *
     * or we found one reservable space in the middle of the list,
     * return the reservation window that we could append to.
     * succeed.
     */

    if ((prev != my_rsv) && (!rsv_is_empty(&my_rsv->rsv_window)))
        rsv_window_remove(sb, my_rsv);

    /*
     * Let's book the whole available window for now.  We will check the
     * disk bitmap later and then, if there are free blocks then we adjust
     * the window size if it's larger than requested.
     * Otherwise, we will remove this node from the tree next time
     * call find_next_reservable_window.
     */
    my_rsv->rsv_start = cur;
    my_rsv->rsv_end = cur + size - 1;
    my_rsv->rsv_alloc_hit = 0;

    if (prev != my_rsv)
        ext3_rsv_window_add(sb, my_rsv);

    return 0;
}

static int alloc_new_reservation(struct ext3_reserve_window_node *my_rsv,
        ext3_grpblk_t grp_goal, struct super_block *sb,
        unsigned int group, struct buffer_head *bitmap_bh)
{
    struct ext3_reserve_window_node *search_head;
    ext3_fsblk_t group_first_block, group_end_block, start_block;
    ext3_grpblk_t first_free_block;
    struct rb_root *fs_rsv_root = &EXT3_SB(sb)->s_rsv_window_root;
    unsigned long size;
    int ret;
    spinlock_t *rsv_lock = &EXT3_SB(sb)->s_rsv_window_lock;

    group_first_block = ext3_group_first_block_no(sb, group);
    group_end_block = group_first_block + (EXT3_BLOCKS_PER_GROUP(sb) - 1);

    if (grp_goal < 0)
        start_block = group_first_block;
    else
        start_block = grp_goal + group_first_block;

    trace_ext3_alloc_new_reservation(sb, start_block);
    size = my_rsv->rsv_goal_size;

    if (!rsv_is_empty(&my_rsv->rsv_window)) {
        /*
         * if the old reservation is cross group boundary
         * and if the goal is inside the old reservation window,
         * we will come here when we just failed to allocate from
         * the first part of the window. We still have another part
         * that belongs to the next group. In this case, there is no
         * point to discard our window and try to allocate a new one
         * in this group(which will fail). we should
         * keep the reservation window, just simply move on.
         *
         * Maybe we could shift the start block of the reservation
         * window to the first block of next group.
         */

        if ((my_rsv->rsv_start <= group_end_block) &&
                (my_rsv->rsv_end > group_end_block) &&
                (start_block >= my_rsv->rsv_start))
            return -1;

        if ((my_rsv->rsv_alloc_hit >
             (my_rsv->rsv_end - my_rsv->rsv_start + 1) / 2)) {
            /*
             * if the previously allocation hit ratio is
             * greater than 1/2, then we double the size of
             * the reservation window the next time,
             * otherwise we keep the same size window
             */
            size = size * 2;
            if (size > EXT3_MAX_RESERVE_BLOCKS)
                size = EXT3_MAX_RESERVE_BLOCKS;
            my_rsv->rsv_goal_size= size;
        }
    }

    spin_lock(rsv_lock);
    /*
     * shift the search start to the window near the goal block
     */
    search_head = search_reserve_window(fs_rsv_root, start_block);

    /*
     * find_next_reservable_window() simply finds a reservable window
     * inside the given range(start_block, group_end_block).
     *
     * To make sure the reservation window has a free bit inside it, we
     * need to check the bitmap after we found a reservable window.
     */
retry:
    ret = find_next_reservable_window(search_head, my_rsv, sb,
                        start_block, group_end_block);

    if (ret == -1) {
        if (!rsv_is_empty(&my_rsv->rsv_window))
            rsv_window_remove(sb, my_rsv);
        spin_unlock(rsv_lock);
        return -1;
    }

    /*
     * On success, find_next_reservable_window() returns the
     * reservation window where there is a reservable space after it.
     * Before we reserve this reservable space, we need
     * to make sure there is at least a free block inside this region.
     *
     * searching the first free bit on the block bitmap and copy of
     * last committed bitmap alternatively, until we found a allocatable
     * block. Search start from the start block of the reservable space
     * we just found.
     */
    spin_unlock(rsv_lock);
    first_free_block = bitmap_search_next_usable_block(
            my_rsv->rsv_start - group_first_block,
            bitmap_bh, group_end_block - group_first_block + 1);

    if (first_free_block < 0) {
        /*
         * no free block left on the bitmap, no point
         * to reserve the space. return failed.
         */
        spin_lock(rsv_lock);
        if (!rsv_is_empty(&my_rsv->rsv_window))
            rsv_window_remove(sb, my_rsv);
        spin_unlock(rsv_lock);
        return -1;      /* failed */
    }

    start_block = first_free_block + group_first_block;
    /*
     * check if the first free block is within the
     * free space we just reserved
     */
    if (start_block >= my_rsv->rsv_start &&
        start_block <= my_rsv->rsv_end) {
        trace_ext3_reserved(sb, start_block, my_rsv);
        return 0;       /* success */
    }
    /*
     * if the first free bit we found is out of the reservable space
     * continue search for next reservable space,
     * start from where the free block is,
     * we also shift the list head to where we stopped last time
     */
    search_head = my_rsv;
    spin_lock(rsv_lock);
    goto retry;
}

static void try_to_extend_reservation(struct ext3_reserve_window_node *my_rsv,
            struct super_block *sb, int size)
{
    struct ext3_reserve_window_node *next_rsv;
    struct rb_node *next;
    spinlock_t *rsv_lock = &EXT3_SB(sb)->s_rsv_window_lock;

    if (!spin_trylock(rsv_lock))
        return;

    next = rb_next(&my_rsv->rsv_node);

    if (!next)
        my_rsv->rsv_end += size;
    else {
        next_rsv = rb_entry(next, struct ext3_reserve_window_node, rsv_node);

        if ((next_rsv->rsv_start - my_rsv->rsv_end - 1) >= size)
            my_rsv->rsv_end += size;
        else
            my_rsv->rsv_end = next_rsv->rsv_start - 1;
    }
    spin_unlock(rsv_lock);
}

static ext3_grpblk_t
ext3_try_to_allocate_with_rsv(struct super_block *sb, handle_t *handle,
            unsigned int group, struct buffer_head *bitmap_bh,
            ext3_grpblk_t grp_goal,
            struct ext3_reserve_window_node * my_rsv,
            unsigned long *count, int *errp)
{
    ext3_fsblk_t group_first_block, group_last_block;
    ext3_grpblk_t ret = 0;
    int fatal;
    unsigned long num = *count;

    *errp = 0;

    /*
     * Make sure we use undo access for the bitmap, because it is critical
     * that we do the frozen_data COW on bitmap buffers in all cases even
     * if the buffer is in BJ_Forget state in the committing transaction.
     */
    BUFFER_TRACE(bitmap_bh, "get undo access for new block");
    fatal = ext3_journal_get_undo_access(handle, bitmap_bh);
    if (fatal) {
        *errp = fatal;
        return -1;
    }

    /*
     * we don't deal with reservation when
     * filesystem is mounted without reservation
     * or the file is not a regular file
     * or last attempt to allocate a block with reservation turned on failed
     */
    if (my_rsv == NULL ) {
        ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh,
                        grp_goal, count, NULL);
        goto out;
    }
    /*
     * grp_goal is a group relative block number (if there is a goal)
     * 0 <= grp_goal < EXT3_BLOCKS_PER_GROUP(sb)
     * first block is a filesystem wide block number
     * first block is the block number of the first block in this group
     */
    group_first_block = ext3_group_first_block_no(sb, group);
    group_last_block = group_first_block + (EXT3_BLOCKS_PER_GROUP(sb) - 1);

    /*
     * Basically we will allocate a new block from inode's reservation
     * window.
     *
     * We need to allocate a new reservation window, if:
     * a) inode does not have a reservation window; or
     * b) last attempt to allocate a block from existing reservation
     *    failed; or
     * c) we come here with a goal and with a reservation window
     *
     * We do not need to allocate a new reservation window if we come here
     * at the beginning with a goal and the goal is inside the window, or
     * we don't have a goal but already have a reservation window.
     * then we could go to allocate from the reservation window directly.
     */
    while (1) {
        if (rsv_is_empty(&my_rsv->rsv_window) || (ret < 0) ||
            !goal_in_my_reservation(&my_rsv->rsv_window,
                        grp_goal, group, sb)) {
            if (my_rsv->rsv_goal_size < *count)
                my_rsv->rsv_goal_size = *count;
            ret = alloc_new_reservation(my_rsv, grp_goal, sb,
                            group, bitmap_bh);
            if (ret < 0)
                break;          /* failed */

            if (!goal_in_my_reservation(&my_rsv->rsv_window,
                            grp_goal, group, sb))
                grp_goal = -1;
        } else if (grp_goal >= 0) {
            int curr = my_rsv->rsv_end -
                    (grp_goal + group_first_block) + 1;

            if (curr < *count)
                try_to_extend_reservation(my_rsv, sb,
                            *count - curr);
        }

        if ((my_rsv->rsv_start > group_last_block) ||
                (my_rsv->rsv_end < group_first_block)) {
            rsv_window_dump(&EXT3_SB(sb)->s_rsv_window_root, 1);
            BUG();
        }
        ret = ext3_try_to_allocate(sb, handle, group, bitmap_bh,
                       grp_goal, &num, &my_rsv->rsv_window);
        if (ret >= 0) {
            my_rsv->rsv_alloc_hit += num;
            *count = num;
            break;              /* succeed */
        }
        num = *count;
    }
out:
    if (ret >= 0) {
        BUFFER_TRACE(bitmap_bh, "journal_dirty_metadata for "
                    "bitmap block");
        fatal = ext3_journal_dirty_metadata(handle, bitmap_bh);
        if (fatal) {
            *errp = fatal;
            return -1;
        }
        return ret;
    }

    BUFFER_TRACE(bitmap_bh, "journal_release_buffer");
    ext3_journal_release_buffer(handle, bitmap_bh);
    return ret;
}

static int ext3_has_free_blocks(struct ext3_sb_info *sbi, int use_reservation)
{
    ext3_fsblk_t free_blocks, root_blocks;

    free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
    root_blocks = le32_to_cpu(sbi->s_es->s_r_blocks_count);
    if (free_blocks < root_blocks + 1 && !capable(CAP_SYS_RESOURCE) &&
        !use_reservation && !uid_eq(sbi->s_resuid, current_fsuid()) &&
        (gid_eq(sbi->s_resgid, GLOBAL_ROOT_GID) ||
         !in_group_p (sbi->s_resgid))) {
        return 0;
    }
    return 1;
}

int ext3_should_retry_alloc(struct super_block *sb, int *retries)
{
    if (!ext3_has_free_blocks(EXT3_SB(sb), 0) || (*retries)++ > 3)
        return 0;

    jbd_debug(1, "%s: retrying operation after ENOSPC\n", sb->s_id);

    return journal_force_commit_nested(EXT3_SB(sb)->s_journal);
}

ext3_fsblk_t ext3_new_blocks(handle_t *handle, struct inode *inode,
            ext3_fsblk_t goal, unsigned long *count, int *errp)
{
    struct buffer_head *bitmap_bh = NULL;
    struct buffer_head *gdp_bh;
    int group_no;
    int goal_group;
    ext3_grpblk_t grp_target_blk;   /* blockgroup relative goal block */
    ext3_grpblk_t grp_alloc_blk;    /* blockgroup-relative allocated block*/
    ext3_fsblk_t ret_block;     /* filesyetem-wide allocated block */
    int bgi;            /* blockgroup iteration index */
    int fatal = 0, err;
    int performed_allocation = 0;
    ext3_grpblk_t free_blocks;  /* number of free blocks in a group */
    struct super_block *sb;
    struct ext3_group_desc *gdp;
    struct ext3_super_block *es;
    struct ext3_sb_info *sbi;
    struct ext3_reserve_window_node *my_rsv = NULL;
    struct ext3_block_alloc_info *block_i;
    unsigned short windowsz = 0;
#ifdef EXT3FS_DEBUG
    static int goal_hits, goal_attempts;
#endif
    unsigned long ngroups;
    unsigned long num = *count;

    *errp = -ENOSPC;
    sb = inode->i_sb;

    /*
     * Check quota for allocation of this block.
     */
    err = dquot_alloc_block(inode, num);
    if (err) {
        *errp = err;
        return 0;
    }

    trace_ext3_request_blocks(inode, goal, num);

    sbi = EXT3_SB(sb);
    es = sbi->s_es;
    ext3_debug("goal=%lu.\n", goal);
    /*
     * Allocate a block from reservation only when
     * filesystem is mounted with reservation(default,-o reservation), and
     * it's a regular file, and
     * the desired window size is greater than 0 (One could use ioctl
     * command EXT3_IOC_SETRSVSZ to set the window size to 0 to turn off
     * reservation on that particular file)
     */
    block_i = EXT3_I(inode)->i_block_alloc_info;
    if (block_i && ((windowsz = block_i->rsv_window_node.rsv_goal_size) > 0))
        my_rsv = &block_i->rsv_window_node;

    if (!ext3_has_free_blocks(sbi, IS_NOQUOTA(inode))) {
        *errp = -ENOSPC;
        goto out;
    }

    /*
     * First, test whether the goal block is free.
     */
    if (goal < le32_to_cpu(es->s_first_data_block) ||
        goal >= le32_to_cpu(es->s_blocks_count))
        goal = le32_to_cpu(es->s_first_data_block);
    group_no = (goal - le32_to_cpu(es->s_first_data_block)) /
            EXT3_BLOCKS_PER_GROUP(sb);
    goal_group = group_no;
retry_alloc:
    gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
    if (!gdp)
        goto io_error;

    free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
    /*
     * if there is not enough free blocks to make a new resevation
     * turn off reservation for this allocation
     */
    if (my_rsv && (free_blocks < windowsz)
        && (free_blocks > 0)
        && (rsv_is_empty(&my_rsv->rsv_window)))
        my_rsv = NULL;

    if (free_blocks > 0) {
        grp_target_blk = ((goal - le32_to_cpu(es->s_first_data_block)) %
                EXT3_BLOCKS_PER_GROUP(sb));
        bitmap_bh = read_block_bitmap(sb, group_no);
        if (!bitmap_bh)
            goto io_error;
        grp_alloc_blk = ext3_try_to_allocate_with_rsv(sb, handle,
                    group_no, bitmap_bh, grp_target_blk,
                    my_rsv, &num, &fatal);
        if (fatal)
            goto out;
        if (grp_alloc_blk >= 0)
            goto allocated;
    }

    ngroups = EXT3_SB(sb)->s_groups_count;
    smp_rmb();

    /*
     * Now search the rest of the groups.  We assume that
     * group_no and gdp correctly point to the last group visited.
     */
    for (bgi = 0; bgi < ngroups; bgi++) {
        group_no++;
        if (group_no >= ngroups)
            group_no = 0;
        gdp = ext3_get_group_desc(sb, group_no, &gdp_bh);
        if (!gdp)
            goto io_error;
        free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
        /*
         * skip this group (and avoid loading bitmap) if there
         * are no free blocks
         */
        if (!free_blocks)
            continue;
        /*
         * skip this group if the number of
         * free blocks is less than half of the reservation
         * window size.
         */
        if (my_rsv && (free_blocks <= (windowsz/2)))
            continue;

        brelse(bitmap_bh);
        bitmap_bh = read_block_bitmap(sb, group_no);
        if (!bitmap_bh)
            goto io_error;
        /*
         * try to allocate block(s) from this group, without a goal(-1).
         */
        grp_alloc_blk = ext3_try_to_allocate_with_rsv(sb, handle,
                    group_no, bitmap_bh, -1, my_rsv,
                    &num, &fatal);
        if (fatal)
            goto out;
        if (grp_alloc_blk >= 0)
            goto allocated;
    }
    /*
     * We may end up a bogus earlier ENOSPC error due to
     * filesystem is "full" of reservations, but
     * there maybe indeed free blocks available on disk
     * In this case, we just forget about the reservations
     * just do block allocation as without reservations.
     */
    if (my_rsv) {
        my_rsv = NULL;
        windowsz = 0;
        group_no = goal_group;
        goto retry_alloc;
    }
    /* No space left on the device */
    *errp = -ENOSPC;
    goto out;

allocated:

    ext3_debug("using block group %d(%d)\n",
            group_no, gdp->bg_free_blocks_count);

    BUFFER_TRACE(gdp_bh, "get_write_access");
    fatal = ext3_journal_get_write_access(handle, gdp_bh);
    if (fatal)
        goto out;

    ret_block = grp_alloc_blk + ext3_group_first_block_no(sb, group_no);

    if (in_range(le32_to_cpu(gdp->bg_block_bitmap), ret_block, num) ||
        in_range(le32_to_cpu(gdp->bg_inode_bitmap), ret_block, num) ||
        in_range(ret_block, le32_to_cpu(gdp->bg_inode_table),
              EXT3_SB(sb)->s_itb_per_group) ||
        in_range(ret_block + num - 1, le32_to_cpu(gdp->bg_inode_table),
              EXT3_SB(sb)->s_itb_per_group)) {
        ext3_error(sb, "ext3_new_block",
                "Allocating block in system zone - "
                "blocks from "E3FSBLK", length %lu",
                 ret_block, num);
        /*
         * claim_block() marked the blocks we allocated as in use. So we
         * may want to selectively mark some of the blocks as free.
         */
        goto retry_alloc;
    }

    performed_allocation = 1;

#ifdef CONFIG_JBD_DEBUG
    {
        struct buffer_head *debug_bh;

        /* Record bitmap buffer state in the newly allocated block */
        debug_bh = sb_find_get_block(sb, ret_block);
        if (debug_bh) {
            BUFFER_TRACE(debug_bh, "state when allocated");
            BUFFER_TRACE2(debug_bh, bitmap_bh, "bitmap state");
            brelse(debug_bh);
        }
    }
    jbd_lock_bh_state(bitmap_bh);
    spin_lock(sb_bgl_lock(sbi, group_no));
    if (buffer_jbd(bitmap_bh) && bh2jh(bitmap_bh)->b_committed_data) {
        int i;

        for (i = 0; i < num; i++) {
            if (ext3_test_bit(grp_alloc_blk+i,
                    bh2jh(bitmap_bh)->b_committed_data)) {
                printk("%s: block was unexpectedly set in "
                    "b_committed_data\n", __func__);
            }
        }
    }
    ext3_debug("found bit %d\n", grp_alloc_blk);
    spin_unlock(sb_bgl_lock(sbi, group_no));
    jbd_unlock_bh_state(bitmap_bh);
#endif

    if (ret_block + num - 1 >= le32_to_cpu(es->s_blocks_count)) {
        ext3_error(sb, "ext3_new_block",
                "block("E3FSBLK") >= blocks count(%d) - "
                "block_group = %d, es == %p ", ret_block,
            le32_to_cpu(es->s_blocks_count), group_no, es);
        goto out;
    }

    /*
     * It is up to the caller to add the new buffer to a journal
     * list of some description.  We don't know in advance whether
     * the caller wants to use it as metadata or data.
     */
    ext3_debug("allocating block %lu. Goal hits %d of %d.\n",
            ret_block, goal_hits, goal_attempts);

    spin_lock(sb_bgl_lock(sbi, group_no));
    le16_add_cpu(&gdp->bg_free_blocks_count, -num);
    spin_unlock(sb_bgl_lock(sbi, group_no));
    percpu_counter_sub(&sbi->s_freeblocks_counter, num);

    BUFFER_TRACE(gdp_bh, "journal_dirty_metadata for group descriptor");
    err = ext3_journal_dirty_metadata(handle, gdp_bh);
    if (!fatal)
        fatal = err;

    if (fatal)
        goto out;

    *errp = 0;
    brelse(bitmap_bh);

    if (num < *count) {
        dquot_free_block(inode, *count-num);
        *count = num;
    }

    trace_ext3_allocate_blocks(inode, goal, num,
                   (unsigned long long)ret_block);

    return ret_block;

io_error:
    *errp = -EIO;
out:
    if (fatal) {
        *errp = fatal;
        ext3_std_error(sb, fatal);
    }
    /*
     * Undo the block allocation
     */
    if (!performed_allocation)
        dquot_free_block(inode, *count);
    brelse(bitmap_bh);
    return 0;
}

ext3_fsblk_t ext3_new_block(handle_t *handle, struct inode *inode,
            ext3_fsblk_t goal, int *errp)
{
    unsigned long count = 1;

    return ext3_new_blocks(handle, inode, goal, &count, errp);
}

ext3_fsblk_t ext3_count_free_blocks(struct super_block *sb)
{
    ext3_fsblk_t desc_count;
    struct ext3_group_desc *gdp;
    int i;
    unsigned long ngroups = EXT3_SB(sb)->s_groups_count;
#ifdef EXT3FS_DEBUG
    struct ext3_super_block *es;
    ext3_fsblk_t bitmap_count;
    unsigned long x;
    struct buffer_head *bitmap_bh = NULL;

    es = EXT3_SB(sb)->s_es;
    desc_count = 0;
    bitmap_count = 0;
    gdp = NULL;

    smp_rmb();
    for (i = 0; i < ngroups; i++) {
        gdp = ext3_get_group_desc(sb, i, NULL);
        if (!gdp)
            continue;
        desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
        brelse(bitmap_bh);
        bitmap_bh = read_block_bitmap(sb, i);
        if (bitmap_bh == NULL)
            continue;

        x = ext3_count_free(bitmap_bh, sb->s_blocksize);
        printk("group %d: stored = %d, counted = %lu\n",
            i, le16_to_cpu(gdp->bg_free_blocks_count), x);
        bitmap_count += x;
    }
    brelse(bitmap_bh);
    printk("ext3_count_free_blocks: stored = "E3FSBLK
        ", computed = "E3FSBLK", "E3FSBLK"\n",
           (ext3_fsblk_t)le32_to_cpu(es->s_free_blocks_count),
        desc_count, bitmap_count);
    return bitmap_count;
#else
    desc_count = 0;
    smp_rmb();
    for (i = 0; i < ngroups; i++) {
        gdp = ext3_get_group_desc(sb, i, NULL);
        if (!gdp)
            continue;
        desc_count += le16_to_cpu(gdp->bg_free_blocks_count);
    }

    return desc_count;
#endif
}

static inline int test_root(int a, int b)
{
    int num = b;

    while (a > num)
        num *= b;
    return num == a;
}

static int ext3_group_sparse(int group)
{
    if (group <= 1)
        return 1;
    if (!(group & 1))
        return 0;
    return (test_root(group, 7) || test_root(group, 5) ||
        test_root(group, 3));
}

int ext3_bg_has_super(struct super_block *sb, int group)
{
    if (EXT3_HAS_RO_COMPAT_FEATURE(sb,
                EXT3_FEATURE_RO_COMPAT_SPARSE_SUPER) &&
            !ext3_group_sparse(group))
        return 0;
    return 1;
}

static unsigned long ext3_bg_num_gdb_meta(struct super_block *sb, int group)
{
    unsigned long metagroup = group / EXT3_DESC_PER_BLOCK(sb);
    unsigned long first = metagroup * EXT3_DESC_PER_BLOCK(sb);
    unsigned long last = first + EXT3_DESC_PER_BLOCK(sb) - 1;

    if (group == first || group == first + 1 || group == last)
        return 1;
    return 0;
}

static unsigned long ext3_bg_num_gdb_nometa(struct super_block *sb, int group)
{
    return ext3_bg_has_super(sb, group) ? EXT3_SB(sb)->s_gdb_count : 0;
}

unsigned long ext3_bg_num_gdb(struct super_block *sb, int group)
{
    unsigned long first_meta_bg =
            le32_to_cpu(EXT3_SB(sb)->s_es->s_first_meta_bg);
    unsigned long metagroup = group / EXT3_DESC_PER_BLOCK(sb);

    if (!EXT3_HAS_INCOMPAT_FEATURE(sb,EXT3_FEATURE_INCOMPAT_META_BG) ||
            metagroup < first_meta_bg)
        return ext3_bg_num_gdb_nometa(sb,group);

    return ext3_bg_num_gdb_meta(sb,group);

}

static ext3_grpblk_t ext3_trim_all_free(struct super_block *sb,
                    unsigned int group,
                    ext3_grpblk_t start, ext3_grpblk_t max,
                    ext3_grpblk_t minblocks)
{
    handle_t *handle;
    ext3_grpblk_t next, free_blocks, bit, freed, count = 0;
    ext3_fsblk_t discard_block;
    struct ext3_sb_info *sbi;
    struct buffer_head *gdp_bh, *bitmap_bh = NULL;
    struct ext3_group_desc *gdp;
    int err = 0, ret = 0;

    /*
     * We will update one block bitmap, and one group descriptor
     */
    handle = ext3_journal_start_sb(sb, 2);
    if (IS_ERR(handle))
        return PTR_ERR(handle);

    bitmap_bh = read_block_bitmap(sb, group);
    if (!bitmap_bh) {
        err = -EIO;
        goto err_out;
    }

    BUFFER_TRACE(bitmap_bh, "getting undo access");
    err = ext3_journal_get_undo_access(handle, bitmap_bh);
    if (err)
        goto err_out;

    gdp = ext3_get_group_desc(sb, group, &gdp_bh);
    if (!gdp) {
        err = -EIO;
        goto err_out;
    }

    BUFFER_TRACE(gdp_bh, "get_write_access");
    err = ext3_journal_get_write_access(handle, gdp_bh);
    if (err)
        goto err_out;

    free_blocks = le16_to_cpu(gdp->bg_free_blocks_count);
    sbi = EXT3_SB(sb);

     /* Walk through the whole group */
    while (start <= max) {
        start = bitmap_search_next_usable_block(start, bitmap_bh, max);
        if (start < 0)
            break;
        next = start;

        /*
         * Allocate contiguous free extents by setting bits in the
         * block bitmap
         */
        while (next <= max
            && claim_block(sb_bgl_lock(sbi, group),
                    next, bitmap_bh)) {
            next++;
        }

         /* We did not claim any blocks */
        if (next == start)
            continue;

        discard_block = (ext3_fsblk_t)start +
                ext3_group_first_block_no(sb, group);

        /* Update counters */
        spin_lock(sb_bgl_lock(sbi, group));
        le16_add_cpu(&gdp->bg_free_blocks_count, start - next);
        spin_unlock(sb_bgl_lock(sbi, group));
        percpu_counter_sub(&sbi->s_freeblocks_counter, next - start);

        free_blocks -= next - start;
        /* Do not issue a TRIM on extents smaller than minblocks */
        if ((next - start) < minblocks)
            goto free_extent;

        trace_ext3_discard_blocks(sb, discard_block, next - start);
         /* Send the TRIM command down to the device */
        err = sb_issue_discard(sb, discard_block, next - start,
                       GFP_NOFS, 0);
        count += (next - start);
free_extent:
        freed = 0;

        /*
         * Clear bits in the bitmap
         */
        for (bit = start; bit < next; bit++) {
            BUFFER_TRACE(bitmap_bh, "clear bit");
            if (!ext3_clear_bit_atomic(sb_bgl_lock(sbi, group),
                        bit, bitmap_bh->b_data)) {
                ext3_error(sb, __func__,
                    "bit already cleared for block "E3FSBLK,
                     (unsigned long)bit);
                BUFFER_TRACE(bitmap_bh, "bit already cleared");
            } else {
                freed++;
            }
        }

        /* Update couters */
        spin_lock(sb_bgl_lock(sbi, group));
        le16_add_cpu(&gdp->bg_free_blocks_count, freed);
        spin_unlock(sb_bgl_lock(sbi, group));
        percpu_counter_add(&sbi->s_freeblocks_counter, freed);

        start = next;
        if (err < 0) {
            if (err != -EOPNOTSUPP)
                ext3_warning(sb, __func__, "Discard command "
                         "returned error %d\n", err);
            break;
        }

        if (fatal_signal_pending(current)) {
            err = -ERESTARTSYS;
            break;
        }

        cond_resched();

        /* No more suitable extents */
        if (free_blocks < minblocks)
            break;
    }

    /* We dirtied the bitmap block */
    BUFFER_TRACE(bitmap_bh, "dirtied bitmap block");
    ret = ext3_journal_dirty_metadata(handle, bitmap_bh);
    if (!err)
        err = ret;

    /* And the group descriptor block */
    BUFFER_TRACE(gdp_bh, "dirtied group descriptor block");
    ret = ext3_journal_dirty_metadata(handle, gdp_bh);
    if (!err)
        err = ret;

    ext3_debug("trimmed %d blocks in the group %d\n",
        count, group);

err_out:
    if (err)
        count = err;
    ext3_journal_stop(handle);
    brelse(bitmap_bh);

    return count;
}

int ext3_trim_fs(struct super_block *sb, struct fstrim_range *range)
{
    ext3_grpblk_t last_block, first_block;
    unsigned long group, first_group, last_group;
    struct ext3_group_desc *gdp;
    struct ext3_super_block *es = EXT3_SB(sb)->s_es;
    uint64_t start, minlen, end, trimmed = 0;
    ext3_fsblk_t first_data_blk =
            le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block);
    ext3_fsblk_t max_blks = le32_to_cpu(es->s_blocks_count);
    int ret = 0;

    start = range->start >> sb->s_blocksize_bits;
    end = start + (range->len >> sb->s_blocksize_bits) - 1;
    minlen = range->minlen >> sb->s_blocksize_bits;

    if (minlen > EXT3_BLOCKS_PER_GROUP(sb) ||
        start >= max_blks ||
        range->len < sb->s_blocksize)
        return -EINVAL;
    if (end >= max_blks)
        end = max_blks - 1;
    if (end <= first_data_blk)
        goto out;
    if (start < first_data_blk)
        start = first_data_blk;

    smp_rmb();

    /* Determine first and last group to examine based on start and len */
    ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) start,
                     &first_group, &first_block);
    ext3_get_group_no_and_offset(sb, (ext3_fsblk_t) end,
                     &last_group, &last_block);

    /* end now represents the last block to discard in this group */
    end = EXT3_BLOCKS_PER_GROUP(sb) - 1;

    for (group = first_group; group <= last_group; group++) {
        gdp = ext3_get_group_desc(sb, group, NULL);
        if (!gdp)
            break;

        /*
         * For all the groups except the last one, last block will
         * always be EXT3_BLOCKS_PER_GROUP(sb)-1, so we only need to
         * change it for the last group, note that last_block is
         * already computed earlier by ext3_get_group_no_and_offset()
         */
        if (group == last_group)
            end = last_block;

        if (le16_to_cpu(gdp->bg_free_blocks_count) >= minlen) {
            ret = ext3_trim_all_free(sb, group, first_block,
                         end, minlen);
            if (ret < 0)
                break;
            trimmed += ret;
        }

        /*
         * For every group except the first one, we are sure
         * that the first block to discard will be block #0.
         */
        first_block = 0;
    }

    if (ret > 0)
        ret = 0;

out:
    range->len = trimmed * sb->s_blocksize;
    return ret;
}